The INTAEditViewNotifier OTA enhancement in 10 Seattle allows drawing into the editor. This can be used to paint the messages directly into the editor.

This could be tricky to write, but would be a /very/ useful warning.

See, eg, http://stackoverflow.com/questions/4509015/should-the-compiler-hint-warn-when-passing-object-instances-directly-as-const-in

var
List : IList<Integer>; // A Spring4D list
...
FreeAndNil(List); // <- bam!

It shouldn't be possible to call Free since you can only call methods defined in an interface on an interfaced type, but FreeAndNil doesn't have any checking and will compile happily with the above code.

If you have a method which declares some constants, and those constants are not used, no warning is generated by Delphi.  IMO there should be a warning, just like for variables that are not used.

Eg,
procedure TForm1.Foo;
const
 A = 1;
 B = 2;
var
 C,
 D : Integer;
begin
 C := B;
 Caption := IntToStr(C);
end;

Delphi warns about unused variable D, but not unused constant A.

The warning W511: Object 'xxx' created in try block is annoying because it is common practice to write code like this:

bla := nil;
blub := TBlub.Create
try
bla := TBla.Create;
// ...
finally
bla.Free;
blub.Free;
end;

I realize that is is difficult to determine whether the object variable is being initialized with nil (how far in front of the try do we look?) but we need a way to reduce the amount of such warnings otherwise they will just be turned off.

(I am sure I am not the first one to notice this, but I the look up did not find anything.)

FixInsightCL -- project=\source\example.dpr --rules=W507;508;C105;C106

Using an index specifier in format statements creates false positive W513 warnings.

ShowMessage(Format('%d %0:d', [1]));//OKAY - output "1 1"
ShowMessage(Format('%0:d %0:d', [1]));//OKAY - output "1 1"
ShowMessage(Format('%0:d %0:d %1:d', [1, 2]));//OKAY - output "1 1 2"
ShowMessage(Format('%0:d %0:d %1:d %d', [1, 2]));//ACTUALLY AN ERROR, because last %d requires a third arguments array item

A constructor that calls another constructor in the same class leads to false positive W504.

type
TFoo = class(TObject)
public
constructor Create;
end;

TBar = class(TFoo)
public
constructor Create;
constructor CreateEx;
end;

//<- http://fixinsight.userecho.com/topic/701447-w504-false-positive-with-objects-inherited-from-tobject/
constructor TFoo.Create;
begin

end;

constructor TBar.Create;
begin
inherited Create;
end;

constructor TBar.CreateEx;//<- False positive W504
begin
Create;
end;

Objects like stringlists should be destroyed by .free; scan for .free for the object if not found flag it
(especially in destroy methods)